Miniaturized mirrors are used for various applications, for example, for optical components in portable telecommunication devices. These mirrors—frequently also called micro-mirrors—may be manufactured from micro-electromechanical structures (MEMS, “micro-electromechanical systems”).
Such micro-mirrors may be based on the capacitive action principle, i.e., a voltage is applied to two electrode elements situated in a predetermined geometry in relation to one another. By varying the voltage, movements of the electrodes in relation to one another may be induced. One of the electrodes is generally fixed on a substrate, while another of the electrodes is freely movable with respect to the substrate at least with respect to one degree of freedom.
In the case of capacitive micro-mirrors, the micro-mirror is typically situated on a substrate and deflected out of the substrate plane via one or more torsion axes. The torsion may be excited via electrodes, which are situated vertically in relation to the substrate, spaced apart from one another, and underneath the micro-mirror. If a control voltage is applied between the electrodes, the electrostatic attraction or repulsion force between the electrodes results in tilting around the torsion axis, which is generally located on the substrate surface, so that the micro-mirror, which lies above it and is mechanically coupled to the tilted electrodes, tilts out of the substrate plane.
The publication U.S. Pat. No. 7,079,299 B1 discloses an electrostatic comb structure in a silicon substrate, which is designed for the purpose of rotating a micro-mirror situated above it around a torsion axis. The publication U.S. Pat. No. 6,694,504 B2 discloses a method for manufacturing a micro-mirror, whose torsional electrostatic drive structure has electrodes, which are vertically etched in a silicon substrate and are vertically offset in relation to one another.
One problem in the capacitive activation of micro-mirrors is to generate the highest possible torques on the twisting electrodes using the lowest possible voltages. In addition, the micro-mirror is to respond already at low operating voltages between the electrodes and is to have a preferably linear response characteristic between control voltage and generated torque.
There is therefore a demand for micro-mirrors to be capacitively actuated, in particular for capacitively operable micro-mirrors, which are to be manufactured simply and cost-effectively, the mechanical robustness of which is improved, and which have an improved linear response behavior having a high efficiency ratio between the drive voltage and the torsion torque.